Method and system for controlling propulsive power output of ship

Abstract

A method and a system for controlling a propulsive power output applied to a propeller shaft of a ship. If a current value of a propulsive power of a propulsive power source equals or falls below a lower power limit value, and/or if a current value of an operational parameter reaches a first/lower parameter limit value, a control unit is configured to: increase a power output of an internal combustion engine of the propulsive power source. Thus, operation of the engine below a lower power limit is avoided.

The invention claimed is: 
     
       1. A method of controlling a propulsive power output applied to a propeller shaft of a ship, the ship comprising a propulsive power source and the propeller shaft, wherein
 the propulsive power source comprises an internal combustion engine connected to the propeller shaft, wherein 
 the method comprises steps of:
 producing a propulsive power by means of the propulsive power source, 
 determining a current value of an operational parameter of the internal combustion engine, the operational parameter being a different parameter than the propulsive power, 
 comparing the current value of the operational parameter with a first parameter limit value, wherein 
 
 the internal combustion engine comprises at least one cylinder arrangement and a turbocharger, wherein 
 the cylinder arrangement comprises a combustion chamber, a cylinder bore, a piston configured to reciprocate in the cylinder bore, a gas inlet connected to the combustion chamber, and a gas outlet connected to the combustion chamber, wherein 
 the gas outlet is connected to a turbine side of the turbocharger and the gas inlet is connected to a compressor side of the turbocharger, wherein 
 at least one sensor for sensing at least one operational parameter of the internal combustion engine is configured for sensing a parameter of the turbocharger, characterised in that 
 the operational parameter is one of:
 an absolute value of a derivative of a rotational speed of the turbocharger, 
 a variation of an amplitude of the rotational speed of the turbocharger, 
 an absolute value of a derivative of a pressure at the outlet at the compressor side of the turbocharger, 
 a variation of an amplitude of the pressure at the outlet at the compressor side of the turbocharger, 
 an energy balance over a turbine of the turbocharger, wherein the method comprises steps of: 
 determining a current value of the propulsive power of the propulsive power source, 
 comparing the current value of the propulsive power with a lower power limit value, and wherein 
 
 if the current value of the propulsive power equals or falls below the lower power limit value, but also if the current value of the operational parameter reaches the first parameter limit value, the method comprises a step of:
 increasing a power output of the internal combustion engine. 
 
 
     
     
       2. The method according to  claim 1 , wherein if the current value of the operational parameter reaches the first parameter limit value, the method comprises a step of:
 increasing the lower power limit value. 
 
     
     
       3. The method according to  claim 2 , comprising a step of:
 indicating visually and/or audibly an increase of the lower power limit value. 
 
     
     
       4. The method according to  claim 1 , comprising a step of:
 determining a current value of a further operational parameter of the internal combustion engine, the further operational parameter being a different parameter than the propulsive power, wherein 
 the method comprises steps of:
 comparing the current value of the propulsive power with an upper power limit value, and 
 comparing the current value of the operational parameter or the current value of the further operational parameter with a second parameter limit value, wherein 
 
 if the current value of the propulsive power equals or exceeds the upper power limit value, but also if the current value of the operational parameter or the current value of the further operational parameter reaches the second parameter limit value, the method comprises a step of:
 reducing the power output of the internal combustion engine. 
 
 
     
     
       5. The method according to  claim 4 , wherein if the current value of the operational parameter or the current value of the further operational parameter reaches the second parameter limit value, the method comprises a step of:
 reducing the upper power limit value. 
 
     
     
       6. The method according to  claim 5 , comprising a step of:
 indicating visually and/or audibly a reduction of the upper power limit value. 
 
     
     
       7. The method according to  claim 4 , wherein the propulsive power source comprises a further internal combustion engine connected to the propeller shaft, wherein
 the step of increasing the power output of the internal combustion engine comprises a step of:
 reducing a power output of the further internal combustion engine. 
 
 
     
     
       8. The method according to  claim 7 , wherein the step of reducing a power output of the internal combustion engine comprises a step of:
 increasing a power output of the further internal combustion engine. 
 
     
     
       9. The method according to  claim 4 , wherein the ship comprises a controllable pitch propeller connected to the propeller shaft, and wherein the step of reducing the power output of the internal combustion engine comprises a step of:
 reducing a pitch of the controllable pitch propeller. 
 
     
     
       10. The method according to  claim 4 , wherein the further operational parameter relates to the turbocharger, and/or to the cylinder arrangement. 
     
     
       11. The method according to  claim 10 , wherein the further operational parameter is one of:
 a rotational speed of the turbocharger, 
 a temperature at the inlet at the turbine side of the turbocharger, 
 a temperature at an outlet at the turbine side of the turbocharger, 
 a pressure at the outlet at the compressor side of the turbocharger. 
 
     
     
       12. The method according to  claim 10 , wherein the further operational parameter is one of:
 a temperature of the cylinder arrangement, or 
 a pressure within the combustion chamber. 
 
     
     
       13. The method according to  claim 10 , wherein the further operational parameter is one of:
 an absolute value of a derivative of the rotational speed of the turbocharger, 
 a variation of an amplitude of the rotational speed of the turbocharger, 
 an absolute value of a derivative of the pressure at the outlet at the compressor side of the turbocharger, 
 a variation of an amplitude of the pressure at the outlet at the compressor side of the turbocharger, 
 an energy balance over a turbine of the turbocharger. 
 
     
     
       14. A system for controlling a propulsive power output applied to a propeller shaft of a ship, the system comprising a propulsive power source and a control arrangement, wherein
 the propulsive power source comprises an internal combustion engine connected to the propeller shaft, wherein 
 the control arrangement comprises a control unit, at least one sensor for sensing at least one operational parameter of the internal combustion engine, and wherein 
 the control unit is configured to:
 determine a current value of an operational parameter of the internal combustion engine utilising the at least one sensor, the operational parameter being a different parameter than the propulsive power, and 
 compare the current value of the operational parameter with a first parameter limit value, wherein 
 
 the internal combustion engine comprises at least one cylinder arrangement and a turbocharger, wherein 
 the cylinder arrangement comprises a combustion chamber, a cylinder bore, a piston configured to reciprocate in the cylinder bore, a gas inlet connected to the combustion chamber, and a gas outlet connected to the combustion chamber, wherein 
 the gas outlet is connected to a turbine side of the turbocharger and the gas inlet is connected to a compressor side of the turbocharger, wherein 
 the at least one sensor for sensing at least one operational parameter of the internal combustion engine is configured for sensing a parameter of the turbocharger, characterised in that 
 the operational parameter is one of:
 an absolute value of a derivative of a rotational speed of the turbocharger, 
 a variation of an amplitude of the rotational speed of the turbocharger, 
 an absolute value of a derivative of a pressure at the outlet at the compressor side of the turbocharger, 
 a variation of an amplitude of the pressure at the outlet at the compressor side of the turbocharger, 
 an energy balance over a turbine of the turbocharger, wherein 
 
 the control arrangement comprises at least one power output measuring device of the propulsive power source, wherein 
 the control unit is configured to:
 determine a current value of a propulsive power of the propulsive power source utilising the power output measuring device, and 
 compare the current value of the propulsive power with a lower power limit value, and wherein 
 
 if the current value of the propulsive power equals or falls below the lower power limit value, but also if the current value of the operational parameter reaches the first parameter limit value, the control unit is configured to:
 increase a power output the internal combustion engine. 
 
 
     
     
       15. The system according to  claim 14 , wherein the control unit is configured to:
 determine a current value of a further operational parameter of the internal combustion engine, the further operational parameter being a different parameter than the propulsive power, wherein 
 the control unit is configured to:
 compare the current value of the propulsive power with an upper power limit value, and 
 compare the current value of the operational parameter or a current value of a further operational parameter with a second parameter limit value, wherein 
 
 if the current value of the propulsive power equals or exceeds the upper power limit, but also if the current value of the operational parameter or the current value of the further operational parameter reaches the second parameter limit value, the control unit is configured to:
 reduce a power output of the internal combustion engine. 
 
 
     
     
       16. The system according to  claim 14 , wherein the at least one sensor for sensing at least one operational parameter of the internal combustion engine is configured for sensing a parameter of the cylinder arrangement. 
     
     
       17. The system according to  claim 15 , wherein the control arrangement comprises visual and/or audible indicating means, wherein if the current value of the operational parameter reaches the first parameter limit value, the control unit is configured to:
 increase the lower power limit value, and 
 indicate via the visual and/or audible indicating means the increase of the lower power limit value. 
 
     
     
       18. The system according to  claim 17 , wherein if the current value of the operational parameter or the current value of the further operational parameter reaches the second parameter limit value, the control unit is configured to:
 reduce the upper power limit value, and 
 indicate via the visual and/or audible indicating means a reduction of the upper power limit value. 
 
     
     
       19. The system according to  claim 14 , wherein the propulsive power source comprises a further internal combustion engine connected to the propeller shaft, wherein
 the control unit is configured to reduce a power output of the further internal combustion engine in order to increase the power output of the internal combustion engine. 
 
     
     
       20. The system according to  claim 19 , wherein the control unit is configured to increase a power output of the further internal combustion engine in order to reduce the power output of the internal combustion engine. 
     
     
       21. The system according to  claim 15 , wherein the ship comprises a controllable pitch propeller connected to the propeller shaft, and wherein the control unit is configured to reduce a pitch of the controllable pitch propeller in order to reduce the power output of the internal combustion engine. 
     
     
       22. The system according to  claim 16 , wherein the at least one sensor is one of:
 a rotational speed sensor of the turbocharger, 
 a pressure sensor of the turbocharger, 
 a temperature sensor of the turbocharger, 
 a temperature sensor of the cylinder arrangement, 
 a pressure sensor of the combustion chamber. 
 
     
     
       23. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the steps of the method according to  claim 1 . 
     
     
       24. A computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method according to  claim 1 .